The present invention relates primarily to the field of purification of polar solvents and miscible aprotic solvents and to methods for reclamation of both the purification agent and the impurities.
In the applicant""s U.S. Pat. No. 5,980,749 which issued Nov. 9, 1999 for an invention entitled xe2x80x9cInclusion Methods for Purifying a Solventxe2x80x9d new inclusive methods for purifying polar solvents were disclosed. These methods employ finely divided layered materials and preferably exfoliated layered materials, homogeneously dispersed in polar solvents to capture, by inclusion between layers, various impurities suspended, contained, mixed, or dissolved within the solvent.
The process disclosed in the ""749 Patent has inherent limitations. For example, in the said process both layered materials that include impurities and layered materials that have included no impurities are consumed. Further, the speed with which the layered material includes impurities is limited in time by the rate at which suspended layered materials can be brought into contact with the impurities contained within the solvent.
Therefore, with respect to the speed of the purification process, it would be beneficial if an excess of layered material in relation to the impurities in the solvent could be utilized in order to provide a higher probability of rapidly contacting suspended particles of layered material with the impurities. However, the opposite condition is true when attempting to minimize consumption of layered material. Ideally, in order to minimize the quantity of layered materials consumed in the purification process, one would exactly match the quantity of layered material utilized, to the quantity of the impurity. In the field, this is usually impractical as the exact quantity and definition of the contaminant may be unknown. Further, valuable materials such as metals, metal salts, metal organic compounds, and organic solvents, and others may be included within layers. It may be economically beneficial to separate these materials from other contaminants and from the layered materials that were utilized to remove them from the solvent.
The process disclosed in the ""749 patent is comprised of the steps of adding layered materials, and preferably exfoliated single molecule thick sheets of layered materials, suspended in a pure form of the solvent, to an impure form of the selected solvent. The process further includes, among others, the steps of agitating the combined materials and separating the settled layered material, which now contains the impurities from the pure solvent.
It is an object of the present application to disclose methods that insure a high probability that the layered materials rapidly contact contaminants and further insures that layered materials that did not include contaminants can be recovered and reused. Further, methods are described that allow impurities, that have been concentrated from a solution by inclusion in layered materials, to be separated from the layered materials in the concentrate so that the layered materials may be reused and/or the impurity may be recovered. Finally, a method is described whereby specific materials included within a mixture of contaminants removed from a solvent by inclusion within xe2x80x9cre-stackedxe2x80x9d layers of a layered material can be selectively removed.
Techniques currently employed to purify solvents by capturing impurities between restacked layers of previously dispersed layered materials require the consumption of both layered materials that have included impurities and layered material that has not included impurities. This use of an excess of layered material may make the inclusion methods for purifying solvents economically untenable in some circumstances. In economic comparisons where the cost of inclusion methods are related to the costs associated with other purification methods, the quantity of layered material used becomes critical.
For example, when compared economically to the cost required to purify a source of drinking water that has a specific type of contaminate, such as sea salt, the inclusion methods requiring an excess of homogenously dispersed suspensions of layered materials, may be more costly than other methods such as reverse osmosis if the layered material is consumed.
It would therefore be beneficial if the excess quantity of layered material could be reused. Further, it would be economically beneficial if selected valuable contaminates could be recovered after they have been removed from the solvent by inclusion between layers of restacked sheets, in order to off-set the cost of purification.
In some situations it may be economically prohibitive to purify a contaminated solvent by conventional methods because of the nature and/or volume of contaminant. For example a tailing pond associated with a mine may contain such a large volume of solvent, contaminated to such a high degree, that processes like reverse osmosis, or distillation would eliminate any profit from the sale of the resource. The recovery and reuse of the exfoliated layered material used in the inclusion process will make it more economically competitive with existing procedures.